In a cellular network, data transmission from a terminal device, such as user equipment (UE for short), to a packet data gateway (PGW for short) is implemented by using an end-to-end bearer (Bearer). Long Term Evolution (LTE for short) is used as an example. A bearer from the UE to the PGW determines a data transmission connection between the UE and the PGW, and the bearer from the UE to the PGW is formed by connecting multiple sections of bearers mapped onto different network nodes. Each section of bearer is identified by quality of service (QoS for short). Service data flows may be filtered to different bearers by using a data flow filter, so that service data flows having a same QoS requirement may be aggregated on a same bearer for transmission.
A process in which a network establishes, modifies, or deletes an end-to-end bearer according to the terminal device and the QoS of the service data flow is a part of session management. In addition to the session management, mobility management on the terminal device is also an important part in the cellular network, and the mobility management mainly includes updating of a location area in which the terminal device is located and paging of the terminal device.
After the LTE is introduced, because mobility management is separately performed on the LTE and Global System for Mobile Communications (GSM)/Wideband Code Division Multiple Access (WCDMA) by using different core network mobility management entities, when the terminal device moves between the LTE and the GSM/WCDMA, location areas of different systems may need to be frequently updated.
In conclusion, in the prior aft, a core network gateway establishes an end-to-end bearer according to the QoS requirement, and maps the service data flow of the terminal device onto the bearer. The core network gateway does not know a resource status of an access network. When the QoS requirement of the service data flow changes, the end-to-end bearer needs to be modified. The end-to-end bearer is bound to an access technology, and cannot support a mode in which service data flows are transmitted by using multiple access technologies and resources of the access technologies are dynamically used according to a resource status. The core network gateway needs to send a downlink data notification to the mobility management entity, so as to trigger paging, and the mobility management entity pages an access network device in a location area registered by the terminal device.